JP2002147351A - Control device for variable displacement compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device preventing a sliding part inside a variable displacement compressor from being poorly lubricated when the device is operated in a high discharge pressure. SOLUTION: A control computer 70 disregards a cooling load and outputs a command to a control valve CV to minimize a discharge capacity of the compressor when the discharge pressure Pd reaches a predetermined value or higher. When the discharge capacity of the compressor comes to a minimum, a refrigerant circulation via an outside refrigerant circuit is stopped and an internal refrigerant circulation via a discharge chamber 22, a crankcase 5, an intake chamber 21 and a compressing chamber 29 is performed for circulating the refrigerant as well as lubricant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling a displacement of a variable displacement compressor which constitutes a refrigerant circuit of a vehicle air conditioner, for example.

[0002]

2. Description of the Related Art In a variable displacement compressor (hereinafter referred to as a compressor) of this kind, the inclination angle of a cam plate is changed by adjusting the pressure of a crank chamber containing a cam plate to which a piston is connected. Some devices have a configuration in which the discharge capacity can be changed between a minimum and a maximum. This pressure adjustment of the crank chamber is performed by a control valve whose valve opening is adjusted based on a command signal from a control computer.

In recent years, a so-called clutchless type compressor which does not include a clutch mechanism such as an electromagnetic clutch on a power transmission path between a drive shaft of the compressor and a vehicle engine which is an external drive source thereof has been put to practical use. Has been The compressor can be provided at a low cost and reduced in weight by not having an expensive and heavy electromagnetic clutch, and can prevent deterioration of drivability because it does not involve an on / off shock of the electromagnetic clutch. There are various advantages.

The above-mentioned clutchless type compressor has an external refrigerant circulation stopping means for stopping the circulation of the refrigerant via the external refrigerant circuit in conjunction with the minimization of the discharge capacity. Then, when cooling is unnecessary, the control computer outputs to the control valve a command signal for minimizing the displacement of the variable displacement compressor. Therefore, it is possible to prevent the refrigerant circulation via the external refrigerant circuit from being stopped by the external refrigerant circulation stop means, thereby preventing unnecessary cooling.The minimum discharge capacity of the compressor allows the discharge chamber, the crank chamber, the suction chamber and Lubrication of each sliding portion can be ensured by the lubricating oil circulating with the refrigerant through the internal refrigerant circulation circuit via the compression chamber.

[0005]

If the discharge pressure in the refrigerant circuit rises excessively, there arises a problem that an excessive load is applied to the piping of the external refrigerant circuit. Therefore, when the discharge pressure information from the discharge pressure sensor becomes equal to or higher than the predetermined value, the control computer outputs a command signal to the control valve until the discharge pressure becomes lower than the predetermined value. Protection control is performed such that the capacity is gradually reduced toward the side where the capacity is reduced (for example, Japanese Patent Laid-Open No.
9-112156).

However, if the excessively increased discharge pressure does not immediately decrease due to a decrease in the discharge capacity of the compressor for some reason, the discharge capacity of the compressor is close to the minimum (not the minimum). In some cases. In order to reduce the power loss of the engine at the time of cooling stop, the clutchless type compressor has a minimum discharge capacity set to be much smaller (near zero) than a compressor with a so-called clutch. Therefore, when the discharge capacity of the compressor is close to the minimum, the amount of the return refrigerant from the external refrigerant circuit becomes small, and particularly, the sliding portion between the piston and the cylinder bore, which is expected to lubricate the lubricating oil contained in the return refrigerant. And other problems such as severe lubrication.

An object of the present invention is to provide a control device which does not cause poor lubrication of a sliding portion inside a variable displacement compressor when a high discharge pressure is supported.

[0008]

According to one aspect of the present invention, there is provided a control valve capable of controlling a valve opening for changing a pressure in a crank chamber based on a command signal.
A discharge pressure detecting means capable of detecting a pressure in a discharge pressure region of the refrigerant circulation circuit, and when discharge pressure information from the discharge pressure detecting means is equal to or more than a predetermined value, the discharge capacity of the variable displacement compressor is increased. Control means for outputting a command signal to be minimized to the control valve.

With this configuration, when the discharge pressure becomes excessive, the discharge capacity of the variable displacement compressor is immediately minimized. When the displacement of the variable displacement compressor is the minimum, the piston does not stroke (when the minimum discharge displacement is set to zero displacement), or the refrigerant circulates through the external refrigerant circuit. The discharge of the refrigerant, that is, the lubricating oil to the cylinder is stopped, and the lubricating oil held inside is circulated (when the minimum discharge capacity is not set to zero capacity). The moving parts do not suffer from poor lubrication.

According to a second aspect of the present invention, in the first aspect, the predetermined value is set to a first predetermined value, and the control means determines whether the discharge pressure has changed from a state lower than the first predetermined value to a state higher than the first predetermined value. The output of the minimization command signal is continued until the discharge pressure becomes equal to or less than a second predetermined value that is less than the first predetermined value.

In this configuration, the threshold value (first predetermined value) of the discharge pressure at which the control means outputs the minimization command signal
And a threshold value (second predetermined value) of the discharge pressure at which the control means stops the output of the minimizing command signal. Therefore, the instantaneous occurrence of the output / stop of the minimization command signal, which tends to occur when only a single threshold value is set, can be avoided, and the displacement control of the compressor can be stabilized. .

According to a third aspect of the present invention, in the first or second aspect, the minimum displacement of the variable displacement compressor is not zero, and the variable displacement compressor is externally linked to the minimum displacement by interlocking with the minimum displacement. An external refrigerant circulation stopping means for stopping the circulation of the refrigerant via the refrigerant circuit is provided.

For example, it is assumed that the minimum displacement of the variable displacement compressor is set to zero by setting the minimum inclination angle of the cam plate to zero. In this case, when the inclination angle of the cam plate becomes zero and the piston does not stroke, in other words, when the compression of the refrigerant gas is not performed, a difference between the pressure in the crank chamber and the pressure in the compression chamber may be generated. This makes it impossible to deviate (increase) the inclination angle of the cam plate from zero. Therefore,
In such a case, a capacity control means is required separately from the crank pressure control mechanism, and the capacity control configuration becomes complicated.

However, in the present invention, since the minimum discharge capacity is not set to zero, the discharge capacity can be released (increased) from the minimum state by controlling the pressure in the crank chamber. Therefore, only the crank pressure control mechanism is required as the capacity control configuration, and the capacity control configuration can be simplified. Further, since the external refrigerant circulation stopping means is provided, if the discharge capacity of the variable displacement compressor is minimized, unnecessary cooling can be prevented even if the minimum discharge capacity is not zero.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the control valve is capable of detecting a pressure at a pressure monitoring point set in the refrigerant circuit, and The pressure-sensitive member is displaced based on the fluctuation, so that the pressure-sensitive mechanism that operates the valve body so that the discharge capacity of the variable displacement compressor is changed to the side that cancels the pressure fluctuation, and the pressure-sensitive member is applied to the pressure-sensitive member. And a setting pressure changing unit that can change a setting pressure serving as a reference for a positioning operation of the valve body by the pressure sensing member by changing a force to be applied by external control.

In this configuration, finer air-conditioning control can be performed as compared with a configuration having no set pressure changing means, that is, a configuration having only a single set pressure. Claim 5
The invention according to any one of claims 1 to 4, wherein the variable displacement compressor is provided with an air supply passage connecting the discharge chamber and the crank chamber, and a bleed passage connecting the crank chamber and the suction chamber, The control valve is characterized in that the pressure in the crank chamber is adjusted by adjusting the opening degree of the air supply passage.

In this configuration, to minimize the displacement of the variable displacement compressor, the control valve increases the degree of opening of the supply passage. Therefore, the air supply passage can be used as a part of a passage for circulating the internal refrigerant, and the configuration of the variable displacement compressor can be simplified.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the drive shaft of the variable displacement compressor is directly connected to an external drive source, and is always driven to rotate when the external drive source operates. It is characterized by.

In this configuration, since a clutch mechanism such as an expensive and heavy electromagnetic clutch or the like is not provided on the power transmission path to the external drive source, the variable displacement compressor can be provided at low cost and reduced in weight. Is possible. In this variable displacement compressor, the compressor is always driven when the external drive source is operated. For this reason, in order to reduce the power loss of the external drive source when the cooling is stopped, the minimum discharge capacity has to be set to be much smaller (near zero) as compared with a so-called clutch-equipped compressor (minimum discharge). If the capacity is not set to zero capacity), a problem that the amount of the return refrigerant from the external refrigerant circuit decreases near the minimum discharge capacity is likely to occur.
Therefore, applying the invention of claim 1 to such a clutchless type variable displacement compressor is particularly effective in achieving the effect.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a control system of a variable displacement type swash plate type compressor provided in a vehicle air conditioner according to the present invention.

(Variable Capacity Swash Plate Compressor) FIGS. 1 and 2
As shown in FIG. 1, a variable displacement swash plate type compressor (hereinafter simply referred to as a compressor) comprises a cylinder block 1, a front housing 2 fixedly joined to the front end thereof, and a cylinder block 1
And a rear housing 4 joined and fixed to the rear end via a valve forming body 3.

A crank chamber 5 is defined in a region surrounded by the cylinder block 1 and the front housing 2. A drive shaft 6 is rotatably disposed in the crank chamber 5. The drive shaft 6 is directly connected to an engine E, which is a traveling drive source of the vehicle as an external drive source, via a power transmission mechanism including a pulley 7 and a belt 8 without using a clutch mechanism such as an electromagnetic clutch. I have. Therefore,
The drive shaft 6 is constantly driven to rotate by the engine E when the engine E is operating. As described above, in the compressor according to the present embodiment, the provision of the expensive and heavy electromagnetic clutch on the power transmission path to the engine E can provide low cost and light weight. Since no on / off shock is caused, drivability can be prevented from deteriorating.

A lug plate 11 is fixed on the drive shaft 6 in the crank chamber 5 so as to be integrally rotatable. A swash plate 12 as a cam plate is provided in the crank chamber 5.
Is housed. The swash plate 12 is supported by the drive shaft 6 so as to be slidable and tiltable. Hinge mechanism 1
3 is interposed between the lug plate 11 and the swash plate 12. Therefore, the swash plate 12 can be rotated synchronously with the lug plate 11 and the drive shaft 6 by the hinge connection with the lug plate 11 via the hinge mechanism 13 and the support of the drive shaft 6, and the drive shaft 6 Can be tilted with respect to the drive shaft 6 while sliding in the axial direction.

A plurality of cylinder bores 1a are formed through the cylinder block 1 so as to surround the drive shaft 6. The single-headed piston 20 is reciprocally accommodated in each cylinder bore 1a. The front and rear openings of the cylinder bore 1a are closed by the valve body 3 and the piston 20, and a compression chamber 29 whose volume changes in accordance with the reciprocation of the piston 20 is defined in the cylinder bore 1a. Each piston 20 is moored to the outer periphery of the swash plate 12 via a shoe 19. Therefore, the rotational movement of the swash plate 12 accompanying the rotation of the drive shaft 6 is converted into the reciprocating linear movement of the piston 20 via the shoe 19.

A suction chamber 21 and a discharge chamber 22 are formed between the valve body 3 and the rear housing 4 respectively. Then, the refrigerant gas in the suction chamber 21 moves from the top dead center position to the bottom dead center side of each piston 20 to the compression chamber 29 via the suction port 23 and the suction valve 24 formed in the valve forming body 3. Inhaled. The refrigerant gas sucked into the compression chamber 29 is compressed to a predetermined pressure by moving from the bottom dead center position of the piston 20 to the top dead center side, and the discharge port 25 and the discharge valve 26 formed in the valve forming body 3 are formed. Through the discharge chamber 22.

(Crank Pressure Control Mechanism) As shown in FIG. 3, the crank pressure control mechanism for controlling the pressure in the crank chamber 5 (crank pressure Pc), which is involved in the tilt angle control of the swash plate 12, has a compression function. It is constituted by a bleed passage 27, an air supply passage 28, and a control valve CV provided in the machine housing. The bleed passage 27 connects the crank chamber 5 and the suction chamber 21 which is a suction pressure (Ps) region. The air supply passage 28 connects the discharge chamber 22 in the discharge pressure (Pd) region and the crank chamber 5, and a control valve CV is provided in the middle thereof.

By adjusting the opening of the control valve CV, the amount of high-pressure discharge gas introduced into the crank chamber 5 through the air supply passage 28 and the crank chamber 5 through the bleed passage 27 are adjusted.
The balance with the amount of gas derived from is controlled, and the crank pressure Pc is determined. In accordance with the change of the crank pressure Pc, the difference between the crank pressure Pc via the piston 20 and the internal pressure of the compression chamber 29 is changed, and the inclination angle of the swash plate 12 (between the virtual plane orthogonal to the drive shaft 6). As a result, the stroke of the piston 20, that is, the displacement is adjusted.

For example, when the opening of the control valve CV is reduced, the crank pressure Pc is reduced, and the crank pressure Pc is reduced.
The difference between the pressure and the internal pressure of the compression chamber 29 via the piston 20 is also reduced, the swash plate 12 is tilted in the direction of increasing the tilt angle, and the displacement of the compressor is increased. FIG. 1 shows a maximum tilt angle state in which the tilt of the swash plate 12 is restricted to abut against the lug plate 11, that is, a maximum discharge capacity state of the compressor.

Conversely, when the opening of the control valve CV is increased, the crank pressure Pc is increased, and the difference between the crank pressure Pc and the internal pressure of the compression chamber 29 via the piston 20 is increased, so that the swash plate 12 Tilts in the direction of decreasing the tilt angle, and the displacement of the compressor is reduced. FIG. 2 shows a minimum inclination angle state in which the inclination of the swash plate 12 is restricted by the minimum inclination angle restriction part 14 provided on the drive shaft 6, that is, a minimum discharge capacity state of the compressor. The minimum inclination angle of the swash plate 12 is set near zero (for example, 2 to 5 degrees).

(Refrigerant circuit) As shown in FIGS. 1 and 2, a refrigerant circuit (refrigeration cycle) of an air conditioner for a vehicle.
Is composed of the compressor and the external refrigerant circuit 30 described above. The external refrigerant circuit 30 includes, for example, a condenser 31, an expansion valve 32 as a pressure reducing device, and an evaporator 33.

Shutoff valve 69 as external refrigerant circulation stop means
Are the discharge chamber 22 of the compressor and the condenser 3 of the external refrigerant circuit 30.
1 on the refrigerant passage. Shut-off valve 69
When the pressure Pd on the discharge chamber 22 side becomes lower than a predetermined value, the refrigerant passage is shut off, and the circulation of the refrigerant via the external refrigerant circuit 30 is stopped.

The shut-off valve 69 may be of a differential pressure valve type which operates by mechanically detecting a pressure difference between before and after the shut-off valve 69, or a control computer 7 which will be described later according to the discharge pressure Pd.
It may be an electromagnetic valve type in which power supply is controlled by 0.
Further, as will be described later, the state where the discharge pressure Pd becomes lower than the predetermined value is brought about by minimizing the discharge capacity of the compressor, so that the shut-off valve 69 is mechanically linked to the minimum inclination angle of the swash plate 12. Even if it is a type, it can fulfill its role sufficiently.

(Control Valve) As shown in FIG.
The V includes an inlet valve portion occupying the upper half thereof, and a solenoid portion 60 as a set pressure changing means occupying the lower half thereof. The inlet valve section adjusts the opening degree (throttle amount) of the air supply passage 28 connecting the discharge chamber 22 and the crank chamber 5.
The solenoid unit 60 is a type of electromagnetic actuator for controlling the operation of the operating rod 40 disposed in the control valve CV based on an external energization control. Operating rod 4
Numeral 0 is composed of a partition 41 as a distal end, a connecting part 42, a valve element 43 at a substantially center, and a guide rod 44 as a proximal end.

The valve housing 45 of the control valve CV
Is composed of a plug body 45a, an upper half body 45b constituting a main outer shell of the inlet side valve section, and a lower half body 45c constituting a main outer shell of the solenoid section 60. A valve chamber 46 and a communication passage 47 are defined in the upper half body 45b of the valve housing 45, and a pressure sensitive chamber 48 is defined between the upper half body 45b and the plug body 45a press-fitted on the upper half body 45b. ing.

An operating rod 40 is provided in the valve chamber 46 and the communication passage 47 so as to be movable in the axial direction (vertically in the drawing). The valve chamber 46 and the communication passage 47 can communicate with each other depending on the arrangement of the operation rod 40. On the other hand, the communication passage 47 and the pressure-sensitive chamber 48 are shut off by the partition 41 of the operating rod 40 fitted in the communication passage 47.

The bottom wall of the valve chamber 46 is formed by the upper end surface of a fixed iron core 62 described later. A port 51 extending in a radial direction is provided on a peripheral wall of the valve housing 45 surrounding the valve chamber 46, and the port 51 connects the valve chamber 46 to the discharge chamber 22 via an upstream portion of the air supply passage 28. A port 52 extending in the radial direction is also provided on the peripheral wall of the valve housing 45 surrounding the communication passage 47, and the port 52 connects the communication passage 47 to the crank chamber 5 through a downstream portion of the air supply passage 28.
To communicate with Therefore, the port 51, the valve chamber 46, the communication passage 47, and the port 52 serve as a control valve passage, and
And a part of an air supply passage 28 that communicates with the crank chamber 5.

The valve body 43 of the operating rod 40 is disposed in the valve chamber 46. The valve body biasing spring 56 is connected to the valve chamber 46.
And urges the valve body 43 downward. The step located at the boundary between the valve chamber 46 and the communication passage 47 forms a valve seat 53, and the communication passage 47 forms a kind of valve hole. When the operating rod 40 moves up from the position shown in FIG. 3 (the lowest position) to the highest position where the valve body 43 is seated on the valve seat 53, the communication path 47 is shut off. That is, the operating rod 40
The valve body portion 43 functions as a valve body capable of arbitrarily adjusting the opening degree of the air supply passage 28.

In the pressure-sensitive chamber 48, a pressure-sensitive member 54 made of a bellows and constituting a pressure-sensitive mechanism is accommodated. The upper end of the pressure sensing member 54 is
Is fixed to the plug 45a. A rod receiver 54a is recessed in the outer bottom wall of the pressure-sensitive member 54, and the tip of the partition 41 of the operating rod 40 is inserted into the rod receiver 54a. The pressure-sensitive member urging spring 55 is housed in the pressure-sensitive member 54 and urges the pressure-sensitive member 54 to extend downward. The pressure-sensitive member 54 is moved downward by the pressure-sensitive member urging spring 55 through the rod receiver 54a.
Pressed against one.

The pressure-sensitive chamber 48 includes a valve housing 45
Is connected to the suction chamber 21 as a pressure monitoring point via a pressure detection port 57 and a pressure detection passage 37 formed in the upper half body 45b. In other words, the suction chamber 21 is
Pressure Ps is introduced.

The solenoid section 60 includes a cylindrical housing cylinder 61 having a bottom. A fixed iron core 62 is fitted to the upper part of the housing cylinder 61, and a solenoid chamber 63 is defined in the housing cylinder 61 by this fitting. A movable iron core 64 is accommodated in the solenoid chamber 63 so as to be movable in the axial direction. A guide hole 6 extending in the axial direction is provided at the center of the fixed iron core 62.
5 is formed, and in the guide hole 65, the operating rod 4
The zero guide rod portion 44 is disposed so as to be movable in the axial direction.

The movable core biasing spring 66 is provided in the solenoid chamber 63.
And urges the movable iron core 64 toward the fixed iron core 62. Therefore, the guide rod portion 44 and the movable iron core 64 are abutted and engaged by the downward urging force of the valve element urging spring 56 and the upward urging force of the movable iron core urging spring 66.
Therefore, the movable iron core 64 and the operating rod 40 always move up and down integrally.

A coil 67 is wound around the fixed iron core 62 and the movable iron core 64 so as to straddle these iron cores 62 and 64. The coil 67 is supplied with a drive signal (command signal) from a drive circuit 71 based on a command from a control computer 70 as a control means in accordance with external information from the external information detection means 72. The coil 67 generates an electromagnetic attractive force (electromagnetic urging force) having a magnitude corresponding to the power supply amount between the movable core 64 and the fixed core 62. The energization of the coil 67 is controlled by adjusting the applied voltage, and the adjustment of the applied voltage employs PWM (pulse width modulation) control.

The external information detecting means 72 includes an air conditioner switch 73 which is an on / off switch of the air conditioner, a temperature setting device 74 for setting the temperature of the passenger compartment, a temperature sensor 75 for detecting the temperature of the passenger compartment, and Pressure P of discharge chamber 22
A discharge pressure sensor 77 for detecting d is provided.

(Operating Characteristics of Control Valve) In the control valve CV, the arrangement position of the operating rod 40, that is, the valve opening is determined as follows.

First, as shown in FIG. 3, when the coil 67 is not energized (duty ratio = 0%), the pressure rod urging spring 55 and the valve element urging spring The action of the downward biasing force of 56 becomes dominant. Therefore,
The operating rod 40 is disposed at the lowermost position, and the valve body 43 fully opens the communication passage 47. Therefore, the crank pressure Pc is
The maximum value that can be taken under the situation at that time,
The piston 20 of the crank pressure Pc and the internal pressure of the compression chamber 29
Is large, the swash plate 12 has a minimum inclination angle, and the displacement of the compressor is minimum.

When the control computer 70 detects that cooling is not required (for example, the air conditioner switch 73 is in an off state) or that cooling is not permitted (a so-called acceleration cut request) such as shifting to a rapidly accelerating state of the vehicle, the control computer 70 sends a control valve CV to the control valve CV. And outputs a minimizing command signal for minimizing the displacement of the compressor. That is, the drive circuit 71 is instructed to set the energization duty ratio to the coil 67 to 0%.

Accordingly, as shown in FIG. 2, the discharge capacity of the compressor is minimized. At this minimum discharge capacity, the pressure Pd on the discharge chamber 22 side in the shutoff valve 69 becomes lower than a predetermined value,
Therefore, the shutoff valve 69 is closed, and the circulation of the refrigerant via the external refrigerant circuit 30 is stopped. That is, the shutoff valve 69
Stops the circulation of the refrigerant via the external refrigerant circuit 30 in conjunction with the minimization of the displacement of the compressor. Also, swash plate 1
Since the minimum inclination angle of 2 is not zero, even if the discharge capacity of the compressor is minimized, the suction of the refrigerant gas from the suction chamber 21 into the compression chamber 29, the compression of the suction refrigerant gas, and the discharge from the compression chamber 29 The discharge of the refrigerant gas into the chamber 22 is performed.

Accordingly, the compression chamber 2 is provided inside the compressor.
9 → discharge chamber 22 → air supply passage 28 → crank chamber 5 → bleed passage 27 → suction chamber 21 → (compression chamber 29), a circulation circuit is formed, and lubricating oil is circulated through the internal refrigerant circulation circuit together with the refrigerant. . For this reason, even if there is no return of the refrigerant containing the lubricating oil from the external refrigerant circuit 30, the lubrication of each sliding portion (for example, between the piston 20 and the cylinder bore 1a) is favorably maintained.

Next, in the control valve CV, the coil 6
7, the minimum duty ratio of the duty ratio variable range (>
0%), the upward electromagnetic biasing force exceeds the downward biasing force of the pressure-sensitive member biasing spring 55 and the valve body biasing spring 56, and the operating rod 40 starts to move upward. In this state, the upward electromagnetic urging force energized by the upward urging force of the movable core urging spring 66 is reduced by the upward urging force of the pressure-sensitive member 54 based on the suction pressure Ps in the pressure-sensitive chamber 48. Pressure-sensitive member urging spring 55 and valve element urging spring 5
6 against the downward pressing force. The valve body 43 of the operating rod 40 is positioned with respect to the valve seat 53 at a position where these vertical biasing forces are balanced.

That is, the control valve CV controls the internal autonomous control of the suction pressure Ps according to the fluctuation of the suction pressure Ps so as to maintain the control target (set suction pressure) of the suction pressure Ps determined by the duty ratio of the current supplied to the coil 67. The structure is such that the operating rod 40 is positioned in a proper manner. Further, the set suction pressure can be externally changed by adjusting the duty ratio of the current supplied to the coil 67.

(Characteristics of the present embodiment) As shown in the graph of FIG. 4, the control computer 70 determines that the discharge pressure Pd information from the discharge pressure sensor 77 is lower than the first predetermined value L1. If it exceeds L1, the cooling load (set temperature information, detected temperature information, etc.) is ignored, and the drive circuit 71 is instructed to set the energization duty ratio to the coil 67 to 0% (minimization command). Therefore, the discharge capacity of the compressor is immediately minimized, and the discharge pressure Pd quickly shifts to a decreasing tendency. Therefore, it is possible to prevent an excessive load based on the high discharge pressure Pd from being applied to the piping and the like of the external refrigerant circuit 30.

The control computer 70 stores the duty ratio instructed to the drive circuit 71 immediately before instructing the minimization of the discharge capacity of the compressor, as a target value (return duty ratio) when the discharge capacity is restored. . Then, when the discharge pressure Pd falls to or below the second predetermined value L2 which is less than the first predetermined value L1, the control computer 70 drives the energization of the coil 67 at the stored return duty ratio. The command is given to the circuit 71, and therefore, the displacement control of the compressor according to the cooling load is restarted.

The present embodiment has the following effects. (1) When the discharge pressure Pd becomes excessively high, the control computer 70 immediately minimizes the discharge capacity of the compressor. Accordingly, the circulation of the refrigerant via the external refrigerant circuit 30 is stopped by the shut-off valve 69, and the internal refrigerant circulation circuit is formed inside the compressor with a minimum non-zero discharge capacity. Therefore, the lubricating oil is not discharged to the outside of the compressor, and the lubricating oil circulating along with the internal refrigerant circulation ensures the proper lubrication of the sliding portion such as between the piston 20 and the cylinder bore 1a. be able to.

(2) The threshold value (first predetermined value L1) of the discharge pressure Pd at which the control computer 70 outputs the minimization command signal, and the discharge pressure at which the control computer 70 stops outputting the minimization command signal The hysteresis characteristic is such that the threshold value of Pd (the second predetermined value L2) is different from each other. Therefore, the instantaneous occurrence of the output / stop of the minimization command signal, which tends to occur when only a single threshold value is set, can be avoided, and the displacement control of the compressor can be stabilized.

(3) For example, in the compressor, the swash plate 1
It is assumed that the minimum discharge capacity is set to zero by setting the tilt angle of No. 2 to zero. In this case, when the inclination angle of the swash plate 12 becomes zero and the piston 20 does not perform a stroke, in other words, when the compression of the refrigerant gas is not performed, the pressure between the pressure Pc of the crank chamber 5 and the pressure of the compression chamber 29 is reduced. A difference cannot be made, and it becomes impossible to separate (increase) the inclination angle of the swash plate 12 from zero. Therefore, in such a case, a capacity control means separate from the crank pressure control mechanism is required, and the capacity control configuration becomes complicated.

However, in this embodiment, since the minimum discharge capacity is not set to zero, the crank pressure Pc
The discharge capacity can be released (increased) from the minimum state by the control of. Therefore, only the crank pressure control mechanism is required as the capacity control configuration, and the capacity control configuration can be simplified.

(4) The control valve CV is provided with a solenoid portion 60 which can externally change a set suction pressure serving as a reference for the positioning operation of the valve body 43 by the pressure-sensitive member 54. Therefore, finer air-conditioning control can be performed as compared with the solenoid valve that does not include the solenoid unit 60, that is, the solenoid that has only a single set suction pressure.

(5) The control valve CV is a so-called inlet control valve for adjusting the crank pressure Pc by adjusting the opening of the air supply passage 28. Therefore, in order to minimize the displacement of the compressor, the control valve CV fully opens the air supply passage 28. Therefore, the air supply passage 28 can be used as a part of a passage for circulating the internal refrigerant, and the configuration of the compressor can be simplified.

(6) The drive shaft 6 is directly connected to the engine E and is always driven to rotate when the engine E is operating.
Therefore, in the compressor of the present embodiment, in order to reduce the power loss of the engine E at the time of cooling stop, the minimum discharge capacity is set to be much smaller (near zero) as compared with a compressor with a so-called clutch. Inevitably, the problem that the amount of the return refrigerant from the external refrigerant circuit 30 decreases near the minimum discharge capacity tends to occur. In other words, embodying the present invention in a clutchless compressor is particularly effective for achieving the effect.

The present invention can be practiced in the following modes without departing from the spirit of the present invention. The control valve CV is not limited to the so-called set suction pressure variable valve in the mode of the above embodiment, and may be, for example, a set discharge pressure variable valve. The set discharge pressure variable valve controls the discharge pressure Pd so as to maintain the control target (set discharge pressure) of the discharge pressure Pd determined by the set pressure changing means.
The valve body is configured to autonomously position the valve body in accordance with the fluctuation of d.

In the refrigerant circuit, two pressure monitoring points are defined as a first pressure monitoring point (for example, a discharge pressure area) and a second pressure monitoring point (for example, a discharge pressure area) lower than the first pressure monitoring point. Set to. The pressure sensing mechanism of the control valve can detect a pressure difference between the first pressure monitoring point and the second pressure monitoring point, and the pressure sensing member is displaced based on a change in the pressure difference between the two pressure monitoring points. Thus, the valve body is operated so that the displacement of the variable displacement compressor is changed so as to cancel the fluctuation of the pressure difference. Therefore, by changing the force applied to the pressure-sensitive member by the set-pressure changing means by external control, the set differential pressure serving as a reference for the positioning operation of the valve element by the pressure-sensitive member is changed.

The internal autonomous configuration (pressure sensing mechanism) is deleted from the control valve CV, and a simple solenoid valve configuration is adopted. The control valve CV may be a so-called control valve that adjusts the crank pressure Pc by adjusting the opening of the bleed passage 27 instead of the air supply passage 28.

The minimum inclination angle of the swash plate 12 is set to zero so that the minimum discharge capacity of the compressor becomes zero. By doing so, the piston 20 does not make a stroke in the minimum discharge capacity state of the compressor, so that the drive shaft 6
Does not perform unnecessary cooling (in other words, discharge of the refrigerant to the external refrigerant circuit 30) even if is rotated, and eliminates the problem of lubrication between the piston 20 and the cylinder bore 1a. Therefore, the shutoff valve 69 can be omitted.

The external information detecting means 72 is provided with a rotational speed sensor for detecting the rotational speed of the drive shaft 6. Then, the control computer 70 is configured to change at least the first predetermined value L1 according to the rotation speed of the drive shaft 6. That is, if the rotational speed of the drive shaft 6, that is, the moving speed of the piston 20, is high even at the same discharge pressure Pd, lubrication between the piston 20 and the cylinder bore 1a becomes severe, and in this case, the control computer 70 Change the value L1 to a lower value. Conversely, the control computer 70
Changes the first predetermined value L1 to a higher value if the rotation speed of the drive shaft 6 is lower. According to this configuration, protection of the air conditioner and satisfying the cooling requirement can be balanced at a high level.

In the above embodiment, the shut-off valve 69 shuts off the discharge side of the compressor. However, the shut-off valve 69 may shut off the suction side. -To embody the control device of a wobble type variable displacement compressor.

The technical idea that can be grasped from the above embodiment is as follows. The variable speed compressor has a rotational speed detecting means capable of detecting the rotational speed of the drive shaft, and the control means controls the rotational speed from the rotational speed detecting means. The control device according to any one of claims 1 to 6, wherein a threshold discharge pressure for outputting a minimization command signal is changed according to the information.

[0067]

As described above in detail, according to the present invention, the sliding portion inside the variable displacement compressor does not suffer from poor lubrication at the time of high discharge pressure.

[Brief description of the drawings]

FIG. 1 is a sectional view of a variable displacement swash plate type compressor.

FIG. 2 is a cross-sectional view of the variable displacement swash plate type compressor in a minimum discharge displacement state.

FIG. 3 is a sectional view of a control valve.

FIG. 4 is a graph illustrating the operation of a control computer.

[Explanation of symbols]

5 ... Crank chamber, 6 ... Drive shaft, 12 ... Swash plate as cam plate, 20 ... Piston, 21 ... Suction chamber, 22 ... Discharge chamber, 27 ... Bleed passage forming internal refrigerant circulation circuit, 28
... Supply passage, 29 ... Compression chamber, 30 ... External refrigerant circuit, 70 ... Control computer as control means, 77 ...
Discharge pressure sensor as discharge pressure detecting means, E: vehicle engine as external drive source, CV: control valve.

Continued on the front page (72) Inventor Takuya Okuno 2-1-1 Toyota-cho, Kariya-shi, Aichi F-term in Toyota Industries Corporation (reference) 3H045 AA04 AA12 AA27 BA12 BA37 BA44 CA02 CA03 CA13 CA29 DA25 DA43 DA47 EA13 EA33 EA38 EA42 3H076 AA06 BB17 BB32 CC05 CC12 CC20 CC61 CC84 CC85

Claims (6)

[Claims] A refrigerant circulation circuit of an air conditioner is formed together with an external refrigerant circuit, and a pressure of a crank chamber for accommodating a cam plate to which a piston is connected is adjusted, thereby changing a tilt angle of the cam plate to change a discharge capacity. Can be changed between a minimum and a maximum, and when the minimum discharge capacity is set to zero capacity, or when the minimum discharge capacity is not set to zero capacity, the external refrigerant at the same minimum discharge capacity A control device for controlling the discharge capacity of a variable displacement compressor having a configuration in which circulation of refrigerant through a circuit is stopped and internal refrigerant circulation is performed through a discharge chamber, a crank chamber, a suction chamber, and a compression chamber. A control valve capable of controlling a valve opening for changing a pressure of the crank chamber based on a command signal; and a discharge capable of detecting a pressure in a discharge pressure region of the refrigerant circuit. Force detection means, and control means for outputting, to the control valve, a command signal for minimizing a discharge capacity of the variable displacement compressor when discharge pressure information from the discharge pressure detection means is equal to or greater than a predetermined value. And a control device comprising: 2. The method according to claim 1, wherein the predetermined value is set to a first predetermined value, and when the discharge pressure is changed from a state lower than the first predetermined value to a value higher than the first predetermined value, the discharge pressure becomes lower than the first predetermined value. Second
2. The control device according to claim 1, wherein the output of the minimization command signal is continued until the signal becomes smaller than or equal to a predetermined value. 3. The minimum displacement of the variable displacement compressor is not zero, but the variable displacement compressor stops the circulation of the refrigerant via the external refrigerant circuit in conjunction with the minimum displacement. The control device according to claim 1, further comprising an external refrigerant circulation stop unit. 4. The control valve is capable of detecting a pressure at a pressure monitoring point set in the refrigerant circuit, and displacing the pressure-sensitive member based on a pressure change at the pressure monitoring point. A pressure-sensitive mechanism that operates a valve element to change the discharge capacity of the variable displacement compressor to the side that cancels the pressure fluctuation; and The control device according to any one of claims 1 to 3, further comprising: a set pressure changing unit configured to change a set pressure serving as a reference of a positioning operation of the valve body by the pressure member. 5. The variable displacement compressor includes an air supply passage connecting the discharge chamber and the crank chamber, and a bleed air passage connecting the crank chamber and the suction chamber. The control device according to any one of claims 1 to 4, wherein the pressure in the crankcase is adjusted by adjusting the degree. 6. The control device according to claim 1, wherein a drive shaft of the variable displacement compressor is directly connected to an external drive source, and is always driven to rotate when the external drive source is operated.